Resource allocation in a wireless network

ABSTRACT

A wireless communication system and method employing channel transport format allocation in a shared uplink channel between a UE and a Node B, and wherein the UE can determine a transport format combination which it can support, by: detecting in the UE a change in transport format combination that the UE can support; and sending to the Node B an indication of transport format combination that the UE can support, whereby efficiency of channel transport format allocation in the system may be improved. A conditional delay mechanism may be employed to reduce signalling overhead. This allows uplink shared channels to be efficiently used by providing a means by which UTRAN (UMTS terrestrial radio access network) is informed of the TFCs within the TFCS which can be used in the uplink by the UE.A wireless network for configuring transport format combinations (TFCs) is disclosed. The wireless network may send to a user equipment (UE) information with an indication of a plurality of TFCs that can be used for uplink transmission The UE may select a TFC and determine if another TFC is supported by a comparison of a transmission power to a maximum UE transmit power. The UE may send an indication that a higher data rate TFC is supported. The UE may then receive, in relation to the indication, an allocation of uplink resources.

Notice: More than one reissue application has been filed for the reissueof U.S. Pat. No. 7,366,094. The reissue application numbers are Ser. No.12/770,172 and the present application.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of UK application GB 0116555.4 filedJul. 6, 2001, titled “Channel transport format allocation in a wirelesscommunication system” by Timothy James Speigth of IPWireless, Inc., thecontents of which are incorporated herein by reference. This applicationis a continuation reissue of U.S. patent application Ser. No. 12/770,172filed Apr. 29, 2010, which is a reissue application of U.S. patentapplication Ser. No. 10/190,458 filed Jul. 5, 2002, which issued as U.S.Pat. No. 7,366,094 on Apr. 29, 2008, which claims the benefit of UKapplication GB 0116555.4 filed Jul. 6, 2001, the contents of which arehereby incorporated by reference herein.

FIELD OF THE INVENTION

This invention relates generally to communication systems, andparticularly (though not exclusively) to ‘3GPP Standard’ communicationsystems when uplink shared channels are employed.

BACKGROUND OF THE INVENTION

In the field of this invention it is known that the ‘3GPP Standard’ (theevolving standard for UMTS--Universal Mobile Telecommunication System)allows user equipment--UE--(e.g., a mobile cellular telephone) toautonomously select the transport format combination (TFC). Thetransport format combinations available to the UE will typicallyrepresent different throughputs. Generally, the TFCs which areassociated with higher throughputs require larger amounts of physicalresources (i.e., more codes with lower spreading factors). The UE willbe signalled with the transport format combination set (TFCS) whichdefines a number of TFCs. The ‘layer 1’ 410 (FIG. 4) processes(governing physical channel allocation and control) in the userequipment (UE) will determine the power required to support these TFCs(all the TFCs in the TFCS) and will decide which ones can be used andwhich require more power than is available and therefore cannot be used.

Layer 1 410 (FIG. 4) then signals the available TFCs to medium accesscontrol (MAC). MAC 415 (FIG. 4) then determines which of the availableTFCs will be used.

When a dedicated channel (DCH) is allocated to a user, it is clearly notpossible to reallocate physical resources that have been allocated tothis user but are not used because of the selected TFC.

However, when shared channels are employed in the uplink it isbeneficial to allocate only the necessary amount of physical resource(number and spreading factor of channelisation codes) that a UE canutilize. This is because the resources that could not be used can bereallocated to other users. In addition, when the UE can exploit morephysical resources (use a higher TFC) it is advantageous to know this inorder to provide the highest user throughputs.

Unfortunately, prior art systems do not allow these two techniques to beused.

A need therefore exists for the abovementioned disadvantage(s) to bealleviated.

STATEMENT OF INVENTION

In accordance with a first aspect of the present invention there isprovided a wireless communication system employing channel transportformat allocation between a radio unit and a base station of the system,and wherein the radio unit can determine a transport format combinationwhich it can support, the system comprising: TFC change detection meansfor detecting in a radio unit a change in transport format combinationthat the radio unit can support; and indication means responsive to theTFC change detection means for sending to the base station an indicationof transport format combination that the radio unit can support, wherebyefficiency of channel transport format allocation in the system may beimproved.

In accordance with a second aspect of the present invention there isprovided a method in a wireless communication system for channeltransport format allocation between a radio unit and a base station ofthe system, in which the radio unit can determine a transport formatcombination which it can support, the system comprising: detecting in aradio unit a change in transport format combination that the radio unitcan support; and sending, responsive to detecting, to the base stationan indication of transport format combination that the radio unit cansupport, whereby efficiency of channel transport format allocation inthe system may be improved.

In accordance with a third aspect of the present invention there isprovided a radio unit for use in a wireless communication systememploying channel transport format allocation between the radio unit anda base station of the system, wherein the radio unit can determine atransport format combination which it can support, the radio unitcomprising: TFC change detection means for detecting a change intransport format combination that the radio unit can support; andindication means responsive to the TFC change detection means forsending to the base station an indication of transport formatcombination that the radio unit can support, whereby efficiency ofchannel transport format allocation in the system may be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

One UMTS communication system supporting signalling of change ofavailable TFCs in uplink shared channels incorporating the presentinvention will now be described, by way of example only, with referenceto the accompanying drawings, in which:

FIG. 1 shows a block diagrammatic representation of a UMTS system inwhich the present invention is used;

FIG. 2 shows a graphical representation of variation of required UE TXpower of three TFCs over time, illustrating when the UE may reportchange in available TFC;

FIG. 3 shows a graphical representation of variation of required UE TXpower of two TFCs over time, illustrating when the UE may report changein available TFC by using a time-to-trigger parameter to reducesignalling overhead; and

FIG. 4 shows a graphical representation of a UE including a MAC and alayer 1 according to embodiments of the invention.

DESCRIPTION OF PREFERRED EMBODIMENT

Referring firstly to FIG. 1, a typical, standard UMTS network (100) isconveniently considered as comprising: a user equipment domain (110),made up of a user SIM (USIM) domain (120) and a mobile equipment domain(130); and an infrastructure domain (140), made up of an access networkdomain (150), and a core network domain (160), which is in turn made upof a serving network domain (170) and a transit network domain (180) anda home network domain (190).

In the mobile equipment domain (130), user equipment UE (130A) receivesdata from a user SIM (120A) in the USIM domain 120 via the wired Cuinterface. The UE (130A) communicates data with a Node B (150A) in thenetwork access domain (150) via the wireless Uu interface. Within thenetwork access domain(150), the Node B (150A) communicates with an RNC(150B) via the Iub interface. The RNC (150B) communicates with otherRNC's (not shown) via the Iur interface. The RNC (150B) communicateswith a SGSN (170A) in the serving network domain (170) via the Iuinterface. Within the serving network domain (170), the SGSN (170A)communicates with a GGSN (170B) via the Gn interface, and the SGSN(170A) communicates with a VLR server (170C) via the Gs interface. TheSGSN (170A) communicates with an HLR server (190A) in the home networkdomain (190) via the Zu interface. The GGSN (170B) communicates withpublic data network (180A) in the transit network domain (180) via theYu interface.

Thus, the elements RNC (150B), SGSN (170A) and GGSN (170B) areconventionally provided as discrete and separate units (on their ownrespective software/hardware platforms) divided across the accessnetwork domain (150) and the serving network domain (170), as shown theFIG. 1.

The RNC (150B) is the UTRAN (UMTS Terrestrial Radio Access Network)element responsible for the control and allocation of resources fornumerous Node B's (150A); typically 50 to 100 Node B's may be controlledby one RNC. The RNC also provides reliable delivery of user traffic overthe air interfaces. RNC's communicate with each other (via the interfaceIur) to support handover and macrodiversity.

The SGSN (170A) is the UMTS Core Network element responsible for SessionControl and interface to the Location Registers (HLR and VLR). The SGSNis a large centralised controller for many RNCs.

The GGSN (170B) is the UMTS Core Network element responsible forconcentrating and tunnelling user data within the core packet network tothe ultimate destination (e.g., internet service provider—ISP).

Consider the following signalling and channel allocation procedure thatmay take place in use of the system. A transport format combination set(TFCS) is signalled to the UE 130A, containing 3 TFCs. The TFCs aremapped to a single channelisation code with spreading factors (SF) 16,8, and 4. A PHYSICAL SHARED CHANNEL ALLOCATION message allocates the UEa single channelisation code at SF4, but layer 1 410 (FIG. 4) at the UEdetermines that the estimated power needed for this TFC is greater thanthe maximum UE transmitter power due to limited UE TX transmittercapability, and so this TFC is indicated as not available to the MAC 415(FIG. 4) TFC selection algorithm. Consequently MAC 415 (FIG. 4) selectsthe TFC mapped to a single channelisation code at SF8. It is clear thatin these circumstances system resources are wasted. Since this is ashared channel rather than a dedicated channel, it is important forhigher layers to know about this situation as the additional resourcespace (2 resource units) could be allocated to other users.

Not only is it necessary to know that only an SF8 is selected (andtherefore there are spare physical resources), it is additionallynecessary to know if, at a later date, the UE can exploit an SF4 (higherthroughput).

In accordance with the present invention, a new RRC measurement, whichis conveniently added to the UE internal measurements set defined in3GPP, is used. This measurement is triggered when there is a change tothe available TFCs that are indicated to MAC 415 (FIG. 4) from layer 1410 (FIG. 4).

The triggering of this report is illustrated in FIG. 2. As can be seen,at time t1 the required UE TX power for TFC 1 exceeds the maximumavailable UE TX power and the UE reports change in available TFC. Next,at time t2 the required UE TX power for TFC 2 exceeds the maximumavailable UE TX power and the UE reports change in available TFC. Then,at time t3 the required UE TX power for TFC 2 falls below the maximumavailable UE TX power and the UE reports change in available TFC.Finally, at time t4 the required UE TX power for TFC 1 falls below themaximum available UE TX power and the UE reports change in availableTFC.

The measurement can be filtered by use of a time-to-trigger parameter soas not to generate excessive measurement reports when the available TFCschange rapidly. That is to say, the available TFCs must change for Ttseconds (the value of the time-to-trigger parameter) continuously beforethe measurement report is sent.

FIG. 3 shows how the use of the time-to-trigger parameter modifies thereports generated by the UE when four threshold crossings events occurat times T1, T2, T3 and T4, similarly to the four threshold crossingsevents at times t1, t2, t3 and t4 in FIG. 2. As can be seen in FIG. 3,at time T1 the required UE TX power for TFC 1 exceeds the maximumavailable UE TX power and (rather than the UE immediately reportingchange in available TFC) a time-to-trigger timer (not shown) is started.At time T2 the required UE TX power for TFC 1 falls below the maximumavailable UE TX power and the timer is reset. At time T3 the required UETX power for TFC 1 exceeds the maximum available UE TX power and thetime-to-trigger timer is again started. After a further period of timeTt when the time-to-trigger timer expires the required UE TX power forTFC 1 still exceeds the maximum available UE TX power and so at thistime the UE reports change in available TFC. It will thus be appreciatedthat use of the time-to-trigger parameter avoids the UE reporting changein available TFC on three of the four possible occasions (T1, T2 and T3)when it would have occurred without its use, and on only the fourthoccasion (T4) does the UE reporting change in available TFC, reducingthe signalling overhead by 75%.

The measurement report generated when this measurement is triggeredcontains the calculated transport format combinations (CTFC) of theavailable TFCs in the TFCS. The UTRAN can map these CTFC to physicalresource and can then allocate physical resource appropriately.

The measurement is only used when the UE is in cell_DCH state.

Example of operation:

Assuming the following

TFCSid=1 contains 3 TFCs.

-   -   TFC 1—maps to single code at SF4    -   TFC 2—maps to single code at SF8    -   TFC 3—maps to single code at SF16

The following steps describe briefly the operation of the newmeasurement report:

-   -   1. UE is in cell_DCH state (operating with an assigned dedicated        channel).    -   2. UE requests uplink resource by sending a PUSCH (Physical        Uplink Shared CHannel) CAPACITY REQUEST message.    -   3. UTRAN responds with PHYSICAL SHARED CHANNEL ALLOCATION        message which allocates a single code at SF4 (enough resource        for TFC1) for a number of frames and TFCSid=1.    -   4. UE RRC configures layer 1 410 (FIG. 4) and MAC 415 (FIG. 4)        with the information indicated by the PHYSICAL SHARED CHANNEL        ALLOCATION message.    -   5. UE determines that it cannot employ TFC1 due to lack of UE TX        power (TFC 2 and TFC 3 can be used). Consequently the available        TFCs reported from layer 1 410 (FIG. 4) to MAC 415 (FIG. 4)        changes and a measurement report is triggered which contains the        CTFC of available TFC.    -   6. UTRAN now knows of this power control limit on available TFCs        so further PHYSICAL SHARED CHANNEL ALLOCATION messages to this        UE are for a single code at SF8. The additional 2 resource        units, freed up by only allocating a single code at SF8, are        allocated to other UEs.    -   7. Channel conditions improve for the UE and the available TFCs        reported from layer 1 410 (FIG. 4) to MAC 415 (FIG. 4) increases        to include TFC1. A measurement report is generated and        consequently UTRAN now knows that this UE can handle TFC1. It is        important that this UE is provided with the highest rate        possible (for example, this UE may be on a high-priced tariff        which guarantees high throughputs), so in further allocations        UTRAN does not share out the 2 resource units freed up in the        step above amongst other users but allocates them to this UE.        Thus, subsequent PHYSICAL SHARED CHANNEL ALLOCATION messages        allocate a single code at SF4.

It will be appreciated that the system and methods described above willtypically be performed by computer software program(s), in the userequipment and/or else where in the system, which may be transferred oncomputer readable data carriers such as magnetic or optical disks (notshown).

It will be understood that the method of signalling change of availableTFCs in uplink shared channels described above provides the followingadvantages: The invention allows uplink shared channels to beefficiently used by providing a means by which UTRAN is informed of theTFCs within the TFCS which can be used in the uplink by the UE.

This enables:

-   -   Spare shared channel physical resources to be allocated to other        shared channel users, so increasing overall throughput.    -   The user to be provided when appropriate with the highest        possible uplink rate that can from time to time be supported.

The invention claimed is:
 1. A method for a wireless communicationsystem using transport format combinations (TFC) for allocatingbandwidth of a shared channel among a plurality of radio units in thesystem, the method comprising: receiving, at a radio unit, a transportformat combination set (TFCS) including a transport format combination(TFC) allocated for use by the radio unit for data transmission;detecting in the radio unit that the radio unit can support a TFC withinthe TFCS different from the allocated TFC; and sending, responsive todetecting, to the base station an indication of the transport formatcombination in the TFCS that the radio unit can support.
 2. The methodas claimed in claim 1, further comprising, conditionally delayingsending the indication, until the detected change in transport formatcombination that the radio unit can support has lasted for more than apredetermined period of time.
 3. The method as claimed in claim 1,wherein the allocated TFC reflects an allocation of an uplink sharedchannel among the plurality of radio units in the system.
 4. The methodas claimed in claim 1, wherein the radio unit is part of a UMTS system.5. The method as claimed in claim 4, wherein the step of detectingcomprises: indicating from physical interface circuitry to medium accesscontrol circuitry a change in transport format combination that theradio unit can support.
 6. The method as claimed in claim 5, wherein thestep of indicating comprises providing, to the base station, calculatedtransport format combinations that the radio unit can support.
 7. Awireless unit for data transmission on an uplink channel shared withother wireless units, the uplink channel shared by allocating atransport format combination (TFC) to the wireless unit from abasestation, the wireless unit comprising: physical interface circuitryconfigured to detect Transport Format Combinations (TFCs) that thewireless unit can use; and media access control circuitry configured toreceive, from the physical interface circuitry, an indication of theTFCs that the wireless unit can use, and to select, for uplinktransmission, a TFC from the TFCs that the wireless unit can use, andwherein the media access control circuitry is also configured to providean indication to the basestation if the selected TFC is not theallocated TFC from the basestation.
 8. The wireless unit of claim 7,further comprising a timer configured to prevent transmission of theindication to the basestation unless the detected change has continuedfor at least a predetermined period of time.
 9. The wireless unit ofclaim 7, wherein the wireless unit is configured to operate in a UMTSsystem.
 10. The wireless unit of claim 7, wherein the physical interfacecircuitry is configured to provide calculated TFCs as the indicationprovided to the media access controller circuitry.
 11. A computerreadable medium comprising program code for a method of allocatingbandwidth of a shared wireless medium, the method comprising: receiving,in a radio unit and from a controller, a transport format combinationrepresentative of an allocation of a shared uplink channel; detecting,in the radio unit, a change in Transport Format Combinations (TFC) thatthe radio unit can use for an uplink transmission; and indicating theTFC change to the controller so that the controller can use theindication for reallocating the shared uplink channel.
 12. A computerreadable medium comprising program code for a method to be implementedin a controller for a wireless communications network that provides foruplink transmissions from a plurality of wireless units on a sharedchannel, the method comprising: formulating a first set of transportformat combinations (a TFCS), for transmission to a wireless unit of theplurality, the first TFCS reflecting an allocation of the shared channelamong the plurality of wireless units, and including an initiallyallocated TFC for uplink transmission by the wireless unit; transmittingthe first TFCS to the wireless unit; receiving an indication from thewireless unit that a calculated set of TFCs that the wireless unit canuse for an uplink transmission differs from the initially allocated TFCin the first TFCS; and modifying the allocation of the shared channelamong the wireless units in response to the indication.
 13. The computerreadable medium of claim 12, the stored method further comprising:determining, based on the indication, that the initially allocated TFCprovides a bandwidth higher than what the wireless unit can presentlyuse; and further comprising reallocating, to other wireless units of theplurality, a difference in bandwidth reflected by the highest bandwidthTFC in the calculated set of TFC and the initially allocated TFC in thefirst TFCS.
 14. The computer readable medium of claim 12, the storedmethod further comprising: determining, based on the indication, thatthe wireless unit can use a higher bandwidth TFC in the first TFCS thanthe initially allocated TFC; and allocating the higher bandwidth TFC tothe wireless unit.
 15. A user equipment (UE) comprising: circuitryconfigured to select a first transport format combination (TFC) from aplurality of TFCs; circuitry configured to determine if a second TFC isavailable based on a maximum UE transmit power, wherein the second TFChas a higher data rate than the first TFC; circuitry configured to senddata based on the first TFC and to send an indication that a higher datarate TFC is supported; and circuitry configured to receive, from awireless network in association with the indication, an allocation ofuplink resources.
 16. The UE of claim 15, wherein the second TFCavailability determination occurs over a plurality of measurementperiods.
 17. The UE of claim 15 further comprising: the circuitryfurther configured to receive a transport format combination set (TFCS);and wherein the second TFC is selected from the TFCS.
 18. The UE ofclaim 15, wherein the allocation of uplink resources is for an uplinkshared channel.
 19. The UE of claim 15, wherein the indication isprovided in a report.
 20. A method performed by a user equipment (UE),the method comprising: selecting, by the UE, a first transport formatcombination (TFC) from a plurality of TFCs; determining, by the UE, if asecond TFC is available based on a maximum UE transmit power, whereinthe second TFC has a higher data rate than the first TFC; sending, bythe UE, data using the first TFC; sending, by the UE, an indication thata higher data rate TFC is supported; receiving, by the UE from awireless network in association with the indication, an allocation ofuplink resources.
 21. The method of claim 20 wherein the second TFCavailability determining occurs over a plurality of measurement periods.22. The method of claim 20 further comprising: receiving, by the UE, atransport format combination set (TFCS); and wherein the second TFC isselected from the TFCS.
 23. The method of claim 20, wherein theallocation of uplink resources is for an uplink shared channel.
 24. Themethod of claim 20, wherein the indication is provided in a report. 25.A wireless network comprising: circuitry configured to send, to a userequipment (UE), information with an indication of a plurality oftransport format combinations (TFCs); and the UE comprising: circuitryconfigured to select a first TFC from the plurality of TFCs; circuitryconfigured to determine if a second TFC is available based on a maximumUE transmit power, wherein the second TFC has a higher data rate thanthe first TFC; circuitry configured to send data based on the first TFCand to send another indication that a higher data rate TFC is supported;and circuitry configured to receive, in association with the anotherindication, an allocation of uplink resources.
 26. The wireless networkof claim 25, wherein the allocation of uplink resources is for an uplinkshared channel.
 27. The wireless network of claim 25 characterized inthat: the wireless network is configured to send a transport formatcombination set (TFCS); and wherein the second TFC is selected from theTFCS.
 28. The wireless network of claim 25, wherein the anotherindication is provided in a report.
 29. A method performed by a wirelessnetwork, the method comprising: sending, by the wireless network to auser equipment (UE), information indicating a plurality of transportformat combinations (TFCs); selecting, by the UE, a first TFC from theplurality of TFCs; determining, by the UE, if a second TFC is availablebased on a maximum UE transmit power, wherein the second TFC has ahigher data rate than the first TFC; sending, by the UE, data using thefirst TFC; sending, by the UE, another indication that a higher datarate TFC is supported; and receiving, by the UE in association with theanother indication, an allocation of uplink resources.
 30. The method ofclaim 29, wherein the allocation of uplink resources is for an uplinkshared channel.
 31. The method of claim 29 further comprising: sending,by the wireless network, a transport format combination set (TFCS); andwherein the second TFC is selected from the TFCS.
 32. The method ofclaim 29, wherein the another indication is provided in a report.